Andrew J. Lovinger, director of the polymers program at the National Science Foundation, offers this explanation:

Andrew J. Lovinger
Andrew J. Lovinger

Teflon is a trademark of DuPont for a plastic material known as polytetrafluoroethylene. The secret to Teflons slick surface lies in the fluorine enveloping its molecules. These fluorine atoms repel almost all other materials, preventing them from adhering to Teflon.

We can use two techniques to make Teflon itself stick to surfaces of items such as pots and pans. The first is "sintering," a process similar to melting, in which the Teflon is heated at a very high temperature and pressed firmly onto a surface. When the material cools down to room temperature, however, chances are it will eventually peel away. Chemically modifying the side of the Teflon that you want to have "stick" yields better results. By bombarding it with ions in a high vacuum under an electric field, or "plasma," we can break away many of the fluorine atoms on the surface that we want to make sticky. We can then substitute other groups, such as oxygen, that adhere strongly to surfaces.

Though perhaps best known as a cookware coating, Teflon has a wide range of applications, from insulating data communications cables to repelling water and stains from clothing and upholstery.

Chemical engineer Jan Genzer of North Carolina State University describes another technique:

Polytetrafluoroethylene (PTFE) can also be chemically modified using a so-called reducing agent to break away the fluorine atoms from the surface in order to make it sticky. The reducing agent breaks the bond between fluorine and carbon, and recombines with the fluorine, leaving a carbon radical. These carbons tend to then pair off with one another, forming what are known as unsaturated hydrocarbons. Because they lack a full complement of electrons, these hydrocarbons are sticky, and thus bond easily to things like metal cooking pots